While 1700MW class Pressurized Water Reactor (PWR) projects like US-APWR are conducted by Mitsubishi Heavy Industry (MHI) now, the size of condenser tube bundle becomes the largest ever constructed by MHI to be accordance with the increased heat rejection rate from the turbine system. Where, it becomes difficult to ignore the condensate sub-cooling and heat transfer deterioration by condensate inundation. Therefore, we have been working on research about the practical application of large-sized condenser since 2008, and tube arrangement optimization is one of the important subjects.
As suitable tube arrangement for a large-sized condenser, the proven streamlined shape tube bundle was proposed, which had been adopted in the fossil fuel power units. In the streamlined shape tube bundle, most steam condenses on tubes under horizontal or downward steam flow conditions. In large tube bundle, the heat transfer deterioration due to inundation apparently occurs. On the other hand, condensate is blown away by the horizontal steam flow, and the effect of inundation would be reduced. For the tube arrangement optimization, the accurate knowledge on heat transfer including the behavior of such condensate under the horizontal steam flow condition is essential. However, most research on steam condensation on tube bundle has been conducted for the downward steam flow but the research for horizontal steam flow condensation is very limited so far (1–5).
In the present research, condensation experiments were conducted by using a horizontal tube bank containing 36 cooling tubes with 12 condensate supply tubes. Steam was horizontally supplied to the tube bank at velocities 15–27m/s at pressures of 8.8kPa. Cooling tubes were made of copper and have an outer diameter of 19.1mm and condensing length of 150mm. In order to clarify the effect of condensate inundation on condensation heat transfer in detail, local heat transfer coefficients and the condensate flow in the tube bank were measured. In this paper, we describe findings on the condensate behavior and heat transfer in horizontal flow obtained by the experiment.